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IPCC AR4 Observed Climate Change
Impacts

Recent warming around the world has caused changes in many physical
and biological systems. The Intergovernmental Panel on Climate Change
Fourth Assessment Report and Rosenzweig et al. (2008) documented
observed responses to climate change across a wide range of systems as
well as regions [1, 2]. In the database, responses in physical systems
include shrinking glaciers in every continent, melting permafrost,
shifts in spring peak river discharge associated with earlier
snowmelt, lake and river warming (with effects on thermal
stratification, chemistry, and freshwater organisms), and increases in
coastal erosion. For terrestrial biological systems, changes
documented in the database include shifts in spring events (e.g.,
earlier leaf unfolding, blooming date, migration, and timing of
reproduction), species distributions, and community structure.
Database observations also demonstrate changes in marine-ecosystem
functioning and productivity, including shifts from cold-adapted to
warm-adapted communities, phenological changes and alterations in
species interactions. In each category, many of the data series are
over 35 years in length.

For the database, observations were selected that (1) demonstrate a
statistically significant trend in change in either direction in
systems related to temperature or other climate change variable as
described by the authors; and (2) contain data for at least 20 years
between 1970 and 2004 (although study periods may extend earlier or
later). For each observation, the data series is described in terms of
system, region, longitude and latitude, dates and duration,
statistical significance, type of impact, and whether or not land use
was identified as a driving factor. System changes are taken from ~80
studies (of which ~75 are new since the IPCC Third Assessment Report)
containing >29,500 data series. Observations in the database are
characterized as a ?change consistent with warming? or a ?change not
consistent with warming,? based on information from the underlying
studies.

The locations of the observed physical and biological changes were
overlaid on observed temperatures from 1970-2004 using two different
gridded observed temperature data sets: HadCRUT3 [3] and GHCN-ERSST
[4]. A spatial analysis showed that the agreement between the patterns
of observed significant changes in natural systems and temperature
change is very unlikely to be due to natural variability. Thus, the
Intergovernmental Panel on Climate Change Fourth Assessment Report and
Rosenzweig et al. (2008) concluded that it is likely that
anthropogenic warming has had a discernable influence on many physical
and biological systems at a global scale.

Figure SPM.1.
Locations of significant changes in data series of physical systems
(snow, ice and frozen ground; hydrology; and coastal processes) and
biological systems (terrestrial, marine, and freshwater biological
systems), are shown together with surface air temperature changes
over the period 1970-2004. A subset of about 29,000 data series was
selected from about 80,000 data series from 577 studies. These met
the following criteria: (1) ending in 1990 or later; (2) spanning a
period of at least 20 years; and (3) showing a significant change in
either direction, as assessed in individual studies. These data
series are from about 75 studies (of which about 70 are new since
the Third Assessment) and contain about 29,000 data series, of which
about 28,000 are from European studies. White areas do not contain
sufficient observational climate data to estimate a temperature
trend. The 2 x 2 boxes show the total number of data series with
significant changes (top row) and the percentage of those consistent
with warming (bottom row) for (i) continental regions: North America
(NAM), Latin America (LA), Europe (EUR), Africa (AFR), Asia (AS),
Australia and New Zealand (ANZ), and Polar Regions (PR) and (ii)
global-scale: Terrestrial (TER), Marine and Freshwater (MFW), and
Global (GLO). The numbers of studies from the seven regional boxes
(NAM, …, PR) do not add up to the global (GLO) totals because
numbers from regions except Polar do not include the numbers related
to Marine and Freshwater (MFW) systems. Locations of large-area
marine changes are not shown on the map. [Working Group II Fourth
Assessment F1.8,
F1.9;
Working Group I Fourth Assessment F3.9b].

Disclaimer: Questions regarding this database should be
addressed to Cynthia Rosenzweig. Part of the European data [5] was
contributed by Annette Menzel. Users should contact her regarding these
data. Their contact emails are included in the data description of the
database.

The original database was constructed at GISS with
contributions from IPCC AR4 WGII Chapter 1 Authors. This version 1.0 of
the database was compiled by a GISS-CIESIN team and was reviewed and
approved for publication at the IPCC Data Distribution Centre (DDC) by
the IPCC Task Group on Data and Scenario Support for Impact and Climate
Analysis (TGICA) 15th meeting at Geneva, Switzerland, on 19-21 November,
2008.